multiply the top by 3 and the bottom by 5 to eliminate the s's
9r-15s=-81
25r+15s=115
add the rows together
34r=34
divide both sides by 34
r=1
plugging in r=1 to either equation
5+3s=23
subtract 5 from both rows
3s=18
s=6
solution: r=1, s=6